9294 + Mcqs in Electronics and Communication Engineering Page 153 McqOptions

7601.	Assertion (A): In Figure, the intercept of the line on y-axis is equal to N (ae + ai), where N is number of atoms/m3, ae is electronic polarizability and ai is ionic polarizability.Reason (R): ae and ai are independent of temperature.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

7602.	When a material becomes a superconductor, its resistivity becomes
A.	very small
B.	zero
C.	about 10% of normal value
D.	about 20% of normal value
Answer» C. about 10% of normal value

Discussion

7603.	In a piezoelectric crystal, the application of mechanical force will cause
A.	plastic deformation of crystal
B.	magnetic dipoles in the crystal
C.	electrical polarization in the crystal
D.	shift in Fermi level
Answer» C. electrical polarization in the crystal

Discussion

7604.	As the temperature of a pure silicon specimen is increased
A.	the number of free electrons increases
B.	the number of holes decreases
C.	the number of holes increases
D.	the number of free electrons and holes increases
Answer» E.

Discussion

7605.	The relationship of hysteresis loss to maximum flux density was first determined by
A.	C. Steinmetz
B.	G.R. Kirchoff
C.	Mr. Laplace
D.	Mr. Ampere
Answer» B. G.R. Kirchoff

Discussion

7606.	In metals the thermal conductivity K and electrical conductivity are related as (K/ T) = L, L is known as
A.	Lattice constant
B.	Lorentz number
C.	Lanevin function
D.	Larmor number
Answer» C. Lanevin function

Discussion

7607.	Assertion (A): When an electron is revolving in its orbit and magnetic field is also present, the angular frequency of electron will be affected by the magnetic field.Reason (R): In the case of electron revolving in its orbit in the presence of magnetic field, the orbital magnetic dipole moment is not affected by the presence of magnetic field.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» D. A is false but R is true

Discussion

7608.	The classes of solid dielectrics are
A.	A, B, C, D, E, F, H
B.	A E B F H C D
C.	Y A E B F H C
D.	A E B F H C
Answer» D. A E B F H C

Discussion

7609.	A 200 turn coil has a self inductance of 10 mH. If the number of turns is doubled, all other quantities remaining the same, the self inductance will be
A.	2.5 mH
B.	5 mH
C.	20 mH
D.	40 mH
Answer» E.

Discussion

7610.	Dielectric constant of transformer oil is about
A.	1
B.	4
C.	10
D.	20
Answer» C. 10

Discussion

7611.	Assertion (A): If WF is Fermi energy, v is velocity of electron and m is mass of electron, then .Reason (R): Conductivity of a metal depends on temperature and impurity concentration.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

7612.	A material which is lightly repelled by a magnetic field is known as
A.	diamagnetic material
B.	non-magnetic material
C.	ferromagnetic material
D.	paramagnetic material
Answer» B. non-magnetic material

Discussion

7613.	Assertion (A): CO2 has no resultant dipole moment but CO has a dipole moment.Reason (R): The structure of CO2 is O = C = O.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

7614.	For a photoconductor with equal electron and hole mobilities and perfect ohmic contacts at the ends, an increase in intensity of optical illumination results in
A.	a change in o.c voltage
B.	a change in s.c current
C.	decrease in resistance
D.	increase in resistance
Answer» D. increase in resistance

Discussion

7615.	A permeable substance is one
A.	which is strong magnet
B.	which is a weak magnet
C.	which is a good conductor
D.	through which magnetic lines of force can pass easily
Answer» E.

Discussion

7616.	Which of the following is the poorest conductor of electricity?
A.	Aluminium
B.	Nichrome
C.	Copper
D.	All of the above
Answer» C. Copper

Discussion

7617.	The magnetic moment in units of Bohr magneton of a ferrous ion in any ferrite is
A.	zero
B.	2
C.	4
D.	6
Answer» D. 6

Discussion

7618.	In molecules of ionic crystals, orientation polarization is zero.
A.	True
B.	False
Answer» B. False

Discussion

7619.	The field pattern of a solenoid is similar to that of bar magnet.
A.	True
B.	False
Answer» B. False

Discussion

7620.	Assertion (A): Silicon is the most favoured semiconductor material.Reason (R): PIV for silicon diode is more than that for germanium diode.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» D. A is false but R is true

Discussion

7621.	Assertion (A): When cathode temperature is increased from 2500 K to 2550 K, thermionic emission current may increase by about 50%.Reason (R): Thermionic emission current T2 e-Ew/kT.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

7622.	Orbital magnetic dipole moment is due to the motion of electron in its orbit around nucleus.
A.	True
B.	False
Answer» B. False

Discussion

7623.	Assertion (A): r can be determined experimentally by measuring the capacitance of a parallel plate capacitor with and without the dielectric.Reason (R): Capacitance of a parallel plate capacitor = .
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

7624.	Assertion (A): In many materials, dielectric polarization causes mechanical distortion.Reason (R): If dielectric polarization causes mechanical distortion then mechanical distortion must cause dielectric polarization.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» D. A is false but R is true

Discussion

7625.	Thermistor is used in
A.	temperature measurement
B.	temperature control
C.	high temperature alarm circuits of devices
D.	all of the above
Answer» E.

Discussion

7626.	In carbon resistor colour code, if the third band is of silver, it indicates
A.	that three zeros are to be added to indicate the resistance value
B.	multiplier is 0.01
C.	multiplier is 0.1
D.	tolerance is 5%
Answer» C. multiplier is 0.1

Discussion

7627.	At a temperature of about 1 K, aluminium is a
A.	conductor
B.	insulator
C.	photoconductor
D.	superconductor
Answer» E.

Discussion

7628.	The dielectric constant of ferroelectric materials can be expressed by the equation
A.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/59-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/59-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/59-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/59-4.png">
Answer» B. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/59-2.png">

Discussion

7629.	Assertion (A): Orbital magnetic moment of an electron in an atom is of the order of 1 Bohr magneton.Reason (R): 1 Bohr magneton = 9.27 x 10-24 A/m2.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

7630.	Assertion (A): For elemental dielectrics, P = NaeEi where N is number of atoms/m3, P is polarization, ae is electronic polarization and Ei is internal electric field.Reason (R): In elemental dielectrics there are no permanent dipoles or ions.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

7631.	The circumference of an electron orbit is equal to integer times the wavelength of electron.
A.	True
B.	False
Answer» B. False

Discussion

7632.	In a specimen of silicon steel, a field strength of 200 A/m causes a flux density of 0.5 T. In a specimen of cast iron, the same H would cause B to be
A.	0.5 T
B.	less than 0.5 T
C.	more than 0.5 T
D.	0.5 T or more or less
Answer» C. more than 0.5 T

Discussion

7633.	In a rare gas, the molecules of some atoms have an excess positive or negative charge. The electric field tends to shift positive ions relative to negative ions. This is known as ionic polarization.
A.	True
B.	False
Answer» B. False

Discussion

7634.	To produce magnetic flux, mmf is necessary.
A.	True
B.	False
Answer» B. False

Discussion

7635.	Assertion (A): Ferromagnetic materials possess ferromagnetic properties only when temperature is less than paramagnetic curie temperature.Reason (R): For a ferromagnetic material for T > f.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

7636.	In terms of classical representation of electrons
A.	an atom is essentially empty
B.	an atom is essentially full
C.	an atom may be essentially empty or full depending on the material
D.	an atom may be essentially empty or full depending on temperature
Answer» B. an atom is essentially full

Discussion

7637.	An iron specimen has r = 1000 when B = 0.3 T. If B = 0.35 T, r
A.	will be 1000
B.	will be less than 1000
C.	will be more than 1000
D.	may be more or less than 1000
Answer» E.

Discussion

7638.	Which solid dielectric has highest temperature limit?
A.	E
B.	H
C.	C
D.	F
Answer» D. F

Discussion

7639.	The class of insulation of impregnated paper is
A.	A
B.	B
C.	C
D.	F
Answer» B. B

Discussion

7640.	Assertion (A): The resistance of a copper specimen changes by about 22% when temperature is increased from room temperature to 700 C.Reason (R): The physical properties of a material are determined mostly by the extent of impurities.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

7641.	An electron is moving in a circular orbit of radius R at angular velocity 0 in a field free space. If a magnetic field B is created, the velocity of electron will be given by the equation
A.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/81-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/81-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/81-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/81-4.png">
Answer» B. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/81-2.png">

Discussion

7642.	If v is the velocity of electron, tc is the average time between collisions, the mean free path = vtc.
A.	True
B.	False
Answer» B. False

Discussion

7643.	As per Bohr's postulate, only those circular orbits are stable for which the angular momentum is equal to an integer times .
A.	True
B.	False
Answer» B. False

Discussion

7644.	For a polyatomic gas, the equation relating dielectric constant r with molecular properties is
A.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/55-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/55-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/55-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/55-4.png">
Answer» B. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/55-2.png">

Discussion

7645.	Permeability is analogous to
A.	resistivity
B.	retentivity
C.	conductivity
D.	coercivity
Answer» D. coercivity

Discussion

7646.	A material has N spins per m3. If Np are the dipoles per m3 parallel to field and Na are the dipoles per m3 anti-parallel to field, the magnetisation is
A.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/87-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/87-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/87-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/87-4.png">
Answer» B. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/87-2.png">

Discussion

7647.	The colour code on a carbon resistor is green-blue-yellow. The tolerance is
A.	5%
B.	10%
C.	20%
D.	30%
Answer» D. 30%

Discussion

7648.	Even at room temperature, an intrinsic semiconductor has some holes. These holes are due to
A.	electron
B.	doping
C.	thermal energy
D.	free electrons
Answer» D. free electrons

Discussion

7649.	Assertion (A): For a magnetic material M = ( r - 1) H, where M is magnetic dipole moment/m3, H is field intensity A/m and r is relative permeability.Reason (R): r can have any value from 0 to hundreds of thousands.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» D. A is false but R is true

Discussion

7650.	If m, v, r are the mass, velocity and radius of orbit of electron and h is Planck's constant, quantum condition for electron's orbit is
A.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/30-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/30-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/30-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/30-4.png">
Answer» C. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/30-3.png">

Discussion

Explore topic-wise MCQs in Engineering.

Assertion (A): In Figure, the intercept of the line on y-axis is equal to N (ae + ai), where N is number of atoms/m3, ae is electronic polarizability and ai is ionic polarizability.Reason (R): ae and ai are independent of temperature.

When a material becomes a superconductor, its resistivity becomes

In a piezoelectric crystal, the application of mechanical force will cause

As the temperature of a pure silicon specimen is increased

The relationship of hysteresis loss to maximum flux density was first determined by

In metals the thermal conductivity K and electrical conductivity are related as (K/ T) = L, L is known as

The classes of solid dielectrics are

A 200 turn coil has a self inductance of 10 mH. If the number of turns is doubled, all other quantities remaining the same, the self inductance will be

Dielectric constant of transformer oil is about

Assertion (A): If WF is Fermi energy, v is velocity of electron and m is mass of electron, then .Reason (R): Conductivity of a metal depends on temperature and impurity concentration.

A material which is lightly repelled by a magnetic field is known as

Assertion (A): CO2 has no resultant dipole moment but CO has a dipole moment.Reason (R): The structure of CO2 is O = C = O.

For a photoconductor with equal electron and hole mobilities and perfect ohmic contacts at the ends, an increase in intensity of optical illumination results in

A permeable substance is one

Which of the following is the poorest conductor of electricity?

The magnetic moment in units of Bohr magneton of a ferrous ion in any ferrite is

In molecules of ionic crystals, orientation polarization is zero.

The field pattern of a solenoid is similar to that of bar magnet.

Assertion (A): Silicon is the most favoured semiconductor material.Reason (R): PIV for silicon diode is more than that for germanium diode.

Assertion (A): When cathode temperature is increased from 2500 K to 2550 K, thermionic emission current may increase by about 50%.Reason (R): Thermionic emission current T2 e-Ew/kT.

Orbital magnetic dipole moment is due to the motion of electron in its orbit around nucleus.

Assertion (A): r can be determined experimentally by measuring the capacitance of a parallel plate capacitor with and without the dielectric.Reason (R): Capacitance of a parallel plate capacitor = .

Assertion (A): In many materials, dielectric polarization causes mechanical distortion.Reason (R): If dielectric polarization causes mechanical distortion then mechanical distortion must cause dielectric polarization.

Thermistor is used in

In carbon resistor colour code, if the third band is of silver, it indicates

At a temperature of about 1 K, aluminium is a

The dielectric constant of ferroelectric materials can be expressed by the equation

Assertion (A): Orbital magnetic moment of an electron in an atom is of the order of 1 Bohr magneton.Reason (R): 1 Bohr magneton = 9.27 x 10-24 A/m2.

Assertion (A): For elemental dielectrics, P = NaeEi where N is number of atoms/m3, P is polarization, ae is electronic polarization and Ei is internal electric field.Reason (R): In elemental dielectrics there are no permanent dipoles or ions.

The circumference of an electron orbit is equal to integer times the wavelength of electron.

In a specimen of silicon steel, a field strength of 200 A/m causes a flux density of 0.5 T. In a specimen of cast iron, the same H would cause B to be

In a rare gas, the molecules of some atoms have an excess positive or negative charge. The electric field tends to shift positive ions relative to negative ions. This is known as ionic polarization.

To produce magnetic flux, mmf is necessary.

Assertion (A): Ferromagnetic materials possess ferromagnetic properties only when temperature is less than paramagnetic curie temperature.Reason (R): For a ferromagnetic material for T &gt; f.

In terms of classical representation of electrons

An iron specimen has r = 1000 when B = 0.3 T. If B = 0.35 T, r

Which solid dielectric has highest temperature limit?

The class of insulation of impregnated paper is

Assertion (A): The resistance of a copper specimen changes by about 22% when temperature is increased from room temperature to 700 C.Reason (R): The physical properties of a material are determined mostly by the extent of impurities.

An electron is moving in a circular orbit of radius R at angular velocity 0 in a field free space. If a magnetic field B is created, the velocity of electron will be given by the equation

If v is the velocity of electron, tc is the average time between collisions, the mean free path = vtc.

As per Bohr's postulate, only those circular orbits are stable for which the angular momentum is equal to an integer times .

For a polyatomic gas, the equation relating dielectric constant r with molecular properties is

Permeability is analogous to

A material has N spins per m3. If Np are the dipoles per m3 parallel to field and Na are the dipoles per m3 anti-parallel to field, the magnetisation is

The colour code on a carbon resistor is green-blue-yellow. The tolerance is

Even at room temperature, an intrinsic semiconductor has some holes. These holes are due to

Assertion (A): For a magnetic material M = ( r - 1) H, where M is magnetic dipole moment/m3, H is field intensity A/m and r is relative permeability.Reason (R): r can have any value from 0 to hundreds of thousands.

If m, v, r are the mass, velocity and radius of orbit of electron and h is Planck's constant, quantum condition for electron's orbit is

Assertion (A): Ferromagnetic materials possess ferromagnetic properties only when temperature is less than paramagnetic curie temperature.Reason (R): For a ferromagnetic material for T > f.